The most important thing states can do when legalizing weed is to resist the urge to tax the shit out of it while simultaneously ensuring that regulations are very strictly enforced. One of the big benefits of legal weed can be depriving organized crime of resources. That only works if legal weed is cost competitive with illegal weed. Alcohol is a great example. It used to be the bread and butter of organized crime, now illegal booze is vanishingly rare in the US. We could do the same thing with weed! One really big problem with a lot of weed laws is they try to do too much.
New York is a great example of how to screw this up. They legalized weed but made several huge mistakes. First, they made it very difficult to get a license and prioritized individuals who had previous marijuana convictions. Sounds great in theory but the issue is people with prior drug convictions often don't have the resources to start new businesses! Then they decided to simply not enforce the law so illegal weed shops popped up everywhere, drowning the legal ones who were actually trying to comply.
Moral of the story is if you want to legalize weed just concentrate on doing that right as so much of the societal benefits rely on the regulations working correctly. If you want to help victims of the drug war too that's great, but it should be a separate measure.